Media captionWATCH: Meet Yoz who built her own Tardis in her living room

For some fans of TV shows knowing the trivia, quoting the best lines and dressing like their heroes is just not enough. They need something more, something bigger, to demonstrate their devotion. Among dedicated Dr Who fans, Whovians, that something more, the ultimate expression of fandom, involves building a Tardis.

It is a not a project for the faint-hearted, said David Lifton who built one for his son Rhys - the Whovian in the family.

"It took an entire spring through summer of evenings and weekends to complete the build from start to finish, probably about five months in all," Mr Lifton told the BBC.

Apart from the sheer graft of cutting wood to make all the parts and then constructing the Tardis (which doubles as a garden shed), the hardest part was finding good plans to work from, Mr Lifton explained. As with many other geek maker projects, the web was invaluable.

One of the main places people share plans, pictures and photos of their project is the tardisbuilders.com website. Part confessional, part parts list, the site is a goldmine for anyone coveting their own blue box.

"I came up with the outline drawings and proportions from a basic diagram I found for one of the original Doctor Who films," he said. This, along with close inspection of the many Tardis toys that Rhys owns, helped refine the final design.

Mr Lifton admits that his Tardis is a bit of a "hybrid" in that it combines elements of the 1960s Peter Brachacki version and the craft David Tennant and Matt Smith have been zipping around in.

Which Who

For many of the faithful that have built their own Tardis, mixing elements from more than one Tardis would be unthinkable. For them, producing an exact copy of a particular Tardis is the reason for undertaking the project.

Michael Pickwoad, the current Dr Who production designer, said matching the show version is tricky because the look of the TV Tardis is not nailed down.

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Rhys Lifton's Tardis doubles as a garden shed when it is not travellling the universe

"From story to story we add bits and pieces," he said.

Some of those changes are demanded by the plot of an episode and mean the exterior of the Tardis changes to reflect where the time-travelling gadget is going.

"Sometimes it's aged over 500 years suddenly," he added.

That would mean the paint would be scuffed and the whole box would look battered to reinforce the idea that it has travelled a long way in time and space.

Then there are the changes that production designers make from series to series or with the introduction of a new Who. To the uninitiated the changes might be subtle, but to those who are trying to recreate a particular Tardis they are crucial.

The changes involve the small windows at the top of the doors, the light on top, the poster on the front, the position of the door handle and lock and the stepping around the roof. And then there is the colour of the paint.

"The colours have changed and its now slightly bluer than it was," said Mr Pickwoad, adding that there might be changes to that colour in the future.

"If I was to do another one, another box, we might paint it a different hue of the same colour," he said.

Time watch

Mr Lifton solved the problem of the paint by writing to Dr Who Magazine and asking them. They wrote back with the RGB (red, green, blue) values that let him get a paint that was close enough.

For Whovian Yoz, who prefers not to use her real name, finding the right colour was a much more exhaustive process. Prior to building her police box Yoz built a dossier of all the different versions and the hues of blue they sported.

She was just as thorough when it came to working out the dimensions of the Tardis she wanted to emulate - the one piloted by Peter Davison.

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Yoz went to great lengths to ensure her Tardis was as accurate as possible

"I planned it in extreme detail," she told the BBC and then produced a thick file of plans, pictures and notes she accumulated while preparing, planning and building.

Her full size Tardis dominates the main room in her flat and doubles as a climbing frame and hang out spot for her cat.

For people who are not Whovians, creating a Tardis might seem strange.

"It seems natural to me to want to have a Tardis," she said, adding that the idea was hard to shake once it was conceived. "I could not stop thinking about it and the only solution, the only way to get this idea out of my head, was to build it. To do it."

So she did, even though taking on such an exacting project was harder for her than for most because she suffers from dyscalculia, a condition that made working out the dimensions of the Tardis tricky. She got around this problem by making full size plans of the Tardis and using those a guide when she was sawing and shaping the parts.

All told, she said, the Tardis has taken her about a year to make and she still is not done.

"I'm still not entirely happy with it," she said. "The final stage is to make it dirty so it looks like it has been used."

When Yoz talks about creating her Tardis it is clear that the building project has had an impact on much more than the internal decor of her flat. It has inspired her to get on with many other things, given her new skills and confidence and changed her life.

When David Lifton talks about his Tardis he mentions how much the achievement meant when he finished it and the way it inspired him to tackle other do it yourself projects.

Other people on the Tardis builders forum say the same. It is not just about what you get at the end of the project, it's about what happens along the way.

It is just like the TV Tardis, whenever and whereever it turns up, lives are profoundly changed, lessons are learned and possibilities are seized.